I can tell EB's from BG/JD's at around 7-9 days free swimming. If your lighting is decent, you will know.
As teqvet said, you can expect up to 25% EBJD from a BGxBG spawn. The remaining will be 50% BG and 25% JD.
As for how many will survive, that really depends on the parents, other fish in the tank and you. Are you hatching baby brine shrimp to feed them?